The present invention relates to an internal combustion engine having a fuel injection system.
Most internal combustion engines in automobiles currently use fuel injection systems to supply fuel to the combustion chambers of the engine. Some fuel injection systems have fuel injectors which inject fuel directly into a combustion chamber of an engine. It is a problem to ensure that such fuel is properly atomised.
Most fuel injection system are designed to meter fuel accurately and are not fuel atomisation devices. It is recognised that a finely atomised fuel spray will improve air fuel mixing and will help reduce engine emissions. It is therefore advantageous to incorporate an atomisation feature into the fuel injector. This is difficult with conventional injectors since if the atomisation process has any variable effect on the pressure difference across the injector this can alter the flow rate of fuel through the injector and cause incorrect fuel quantities to be delivered to the engine. Therefore, choosing an effective atomisation process is very limited with the conventional fuel injection systems and the current “state of the art” injection systems overcome this problem by using a complex highly controlled high pressure fuel system where the high kinetic energy in the fuel can aid atomisation.
The sophisticated and highly developed fuel injection systems currently available are ideal for use in internal combustion engines in automobiles. However, there are many other applications for internal combustion engines where such a level of sophistication is not appropriate and too costly. For instance, small single cylinder engines as used for lawn mowers, chain saws, small generators, mopeds, scooters, etc are built to very tight cost targets and so cannot afford the cost of a sophisticated fuel injection system nor the additional power required to run a fuel pump. To date, such small engines have used traditional carburettor technology and relied on a gravity fed fuel supply. However, it is now the case that such small engines will face the same type of exhaust gas emission legislation as the engines in automobiles and so must be modified in such a way as to meet emissions targets. Therefore, a cheap and simple system of fuel injection is required for such small engines.